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Mars
atmosphere history
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Venus,
Earth, Mars probably started out about the same
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First
no atmosphere, then volcanos spew out gas
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Lots
of H2O, CO2, N2 in atmosphere
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Greenhouse
effect from H2O, CO2
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Water
clouds, rain, oceans
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Venus
too hot kept water vapor in atmosphere
-
runaway
greenhouse effect
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Mars
too cold, water rained down
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CO2
dissolves in liquid water
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H2O
+ CO2 + rock = carbonate rocks (limestone)
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Martian
CO2 and water vapor depleted
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Greenhouse
effect becomes less efficient (smaller blanket)
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Gets
colder, less water evaporates...
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reverse
runaway Greenhouse effect
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Earth
just right: has mild Greenhouse effect
-
moderated
by O/CO2 balance
-
without
greenhouse effect, Earth would be 35o C cooler (frozen)
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